I am aware this has been discussed many times and the consensus is that all cars are prone to cracking. I was about to fill my cavity with structural foam when I ran an endoscope inside the cavity of my 2006 M3, and I found something unexpected.
According to BMW's service bulletin to address the RACP, there should be one hole on each side and you'd have to drill one in the middle. Mine already had another hole, offset towards the driver side. This got my curiosity: "is it a coincidence that BMW drilled another hole closer to the side that's prone to crack?)
Fig 1. Offset hole and reinforcement plate.
So I took my endoscope and looked into the cavity from the second hole in fig. 1. I found out that the space that the tis bulletin advises to fill with structural foam was sealed off from the right side of the cavity by a large metal plate that seems to be epoxied in. I tried to illustrate what I found beneth in fig. 1 in red: the metal plat seals off the left side from the right side, and extends towards the RACP mounting points. The bend in the plate has reinforcement which seems to indicate that it is a structural part.
Fig 2. Metal plate inside the cavity, seen from hole 3 following the eye symbol in fig.1, the picture is upside-down. Some epoxy (blue) seems to be fixating the plate to the body metal.
Fig 3. The plate (in black) seems to have a structural design
Fig 4. The plate is also screwed in the top (the "roof" of the cavity where the RACP is mounted)
Fig 5. Photo taken with phone from top of hole 2 showing the plate (in black) and the epoxy that seems to fixate it in the cavity (blue). This photo is also showing the bend and how it looks structural.
Very interestingly, this only exists on the driver side. There is no such plate on the passenger side.
What are we looking at here? Anyone has seen this before? I don't mean to spread disinformation or rumors, I'm just curious and this seems to be reinforcing the RACP. I had never heard of this before. I heard about additional spot-welds in 2001+ models but nothing like this. I know that older cars (2003 for example) don't have this. Would this be a late review of the chassis by BMW?
My car, a 2006, has seen a few track days and some hard driving and shows no sign of failure, including no popped spot welds or apparent hairline cracks (I have not removed the subframe to look under the bushings).
Cheers,
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